This invention relates generally to certain gypsum-based, dry mix-type joint compounds, to compositions employing these dry mix-type joint compounds, to methods for applying the subject compositions in filling and finishing the joint formed between adjacent drywall panels.
As described in U.S. Pat. No. 5,079,042, drywall or gypsum board is used in the form of panels for interior walls of buildings, and has largely replaced plaster in both commercial and residential construction. Thus, commercial drywall panels which are 4'.times.8', 4'.times.9' or 10'.times.12' in size, but can be up to 8'.times.24', are nailed to wood studs with their longer dimension positioned horizontally.
U.S Pat. No. 5,041,333 discloses a continuous process for the producing of exemplary drywall panels or gypsum board. These boards are of variable yet predictable density, wherein a fibrous form of stucco produced from gypsum crystals of fibers is combined with standard calcined gypsum and formed into the board. The density of the resultant board varies inversely with the content of fibrous stucco. The process yields lightweight board suitable as standard wallboards and inorganic insulating boards.
U.S. Pat. No. 4,126,599 discloses a water-resistant shaped gypsum panel comprising (A) calcium sulfate dihydrate formed by hardening of calcium sulfate capable of hydration reaction, (B) a calcium type filler for filling up spaces among crystalline particles of said calcium sulfate dihydrate and (C) a water-insoluble or hardly water-soluble salt of a polybasic acid having a second stage dissociation constant of 10.sup.-3 to 10.sup.-10, especially 10.sup.-4 to 10.sup.-9, as measured at 25 deg. C.
U.S. Pat. No. 4,174,230 discloses a gypsum composition comprising: (A) a lightweight spherical gypsum and (B) at least one binder selected from the group consisting of a water-soluble organic polymer, a water-dispersible organic polymer, a water-soluble inorganic compound, a water-dispersion medium colloid forming inorganic compound, a water-hardenable compound and a mixture thereof. This gypsum composition provides a gypsum molded product which is lightweight and, at the same time, has great mechanical strength.
U.S. Pat. No. 4,350,533 discloses a rapid reaction of high alumina cement, gypsum, lime and water produces hydraulic cementitious compositions in which the only significant factor contributing to strength during the very early stages of hydration (i.e., a few minutes to a few hours) is the formation of an amount of ettringite equal to from about 40% to about 60% of the weight the paste of water, the high alumina cement, the gypsum source, and the lime source. A substantially impermeable concrete having a 4-hour compressive strength of about 8000 p.s.i. may be produced from the cement powder of this invention.
U.S Pat. No. 4,560,413 discloses a hardened cement material having enhanced flexural strength, heat resistance, and water resistance prepared from a cement composition. The cement composition comprises 100 parts by weight of a hydraulic cement material containing .gamma.-dicalcium silicate (.gamma.-C.sub.2 S), preferably in an amount of 1% by weight or more, and 1 to 20 parts by weight of a water-dispersible polymeric material. The cement composition is mixed with 5 to 25 parts by weight of water by a molding procedure and by a heat-hardening procedure at a temperature of 40 degrees C. to 180 degrees C. while controlling the relative humidly to 20% to % and/or applying a pressure of 5 to 15 atmospheres.
U.S. Pat. No. 4,729,853 discloses a flame-retarding sealing compounds based on hydraulic binders. The sealing compounds include hydraulic binders such as gypsum, dehydratable aluminum fillers and melamines.
U.S. Pat. No. 4,746,365 this invention relates to improved aluminous cement/gypsum compositions that contain polymer latex emulsions or compounds to produce self-curing, crack-free, fast-setting, high early strength, high bonding, water resistant, durable, cementitious mixtures for finishing, coating, plastering, stucco, rigid insulation protection, topping, resurfacing, patching, mortaring, tile grouting, concrete, and the like.
U.S. Pat. No. 4,846,889 discloses a polymer blend useful in thin-bed mortar compositions comprising a water-soluble cellulose ether and a water-insoluble, but water-dispersible, polymer. The water insoluble, but water-dispersible polymer can include an unneutralized polyacrylic acid that is lightly crosslinked or methylcellulose with a viscosity from about 50 cps to about 150,000 cpa, provided the polymeric blend containing methylcellulose is employed in a medium that has a pH of about 12 or greater, although a pH of less than 12 is workable, but is dependent upon the methoxyl content of the methylcellulose. The polymeric blend extends the working time of the composition in which it is employed.
The joint between the adjacent horizontal edges of two adjacent gypsum or drywall panels located one above the other must be filled with an appropriate joint compound in order to hide the joint between the two panels and to develop a flat wall surface from the floor to the ceiling. Gypsum-based dry mix type joint compounds have been used successfully in Europe for many years to fill and finish such joints. This is contrary to the North American practice of using paper or fiberglass tape on all drywall seams and angles.
U.S. Pat. No. 5,079,024 discloses a system for finishing the joint between abutting panels of drywall by applying a joint compound comprising mostly gypsum plaster together with (a) fillers such as limestone, mica, and perlite, (b) binders such as clay, natural starch, synthetic starch, CMC and vinyl binders, and (c) a small amount of acrylic monofilament fibers which are about 4 mm to 10 mm longer.
However, it has determined that the joint compound manufactured by the assignee of U.S. Pat. No. 5,079,024, Solid Products, Inc., under hot and dry atmospheric conditions will shrink substantially, and will exhibit substantially reduced flexural strength.
Accordingly, a need remains for dry mix-type joint compounds and compositions therefrom which, when applied in a drywall panel joint, exhibit high flexural strength, minimum shrinkage, and substantially no visible cracking under very hot and dry surrounding atmospheric conditions.